In recent years, the development of Ceramic Matrix Composites (CMC), a type of fiber-reinforced composite materials, has been being promoted. The CMC is a composite material which is ceramic fibers reinforced with a base material (matrix) and is characterized by light weight and excellent heat resistance. The use of the CMC as, for example, aircraft engine components by utilizing these characteristics is being examined and its practical use is currently being promoted. A significant improvement in fuel efficiency can be expected by using the CMC as the aircraft engine components.
A general forming process of the CMC is described as follows. Firstly, about several hundreds of ceramic fibers are tied together to make fiber bundles and these fiber bundles are woven to manufacture a woven fabric. Methods for weaving the fiber bundles include, for example, three-dimensional weaving or plain weaving. The three-dimensional weaving is a method for manufacturing the woven fabric by weaving the fiber bundles in three directions, that is, XYZ-directions and the plain weaving is a method for manufacturing the woven fabric by weaving the fiber bundles in two directions, that is, XY-directions.
After the woven fabric is manufactured, matrixes are formed by means of CVI (Chemical Vapor Infiltration) and PIP (Polymer Impregnation and Pyrolysis); and lastly, machining, surface coating, and so on are performed, thereby forming the CMC. Under this circumstance, orientations of the fiber bundles of the then-formed CMC significantly influence the strength of the CMC.
Specifically speaking, when the fiber bundles wind at places where they should be straight, or when the fiber bundles generally deviate from their reference axis where they should originally be located, or when the fiber bundles break in the middle of the CMC forming process, the strength of the CMC degrades. On the other hand, when the fiber bundles are properly arranged in certain directions without winding, deviating, or breaking, high strength and excellent heat resistance are achieved. Therefore, orientations of the fiber bundles are evaluated in order to check if the strength of the formed CMC is sufficient or not.
PTL 1 discloses an orientation analysis method for acquiring a binary image by binarizing a slice image of a resin molded product, acquiring a power spectrum image by performing Fourier transformation of this binary image, and determining a main axial direction of an ellipse perpendicular to an ellipse drawn by this power spectrum image to be an orientation direction of a filler (fibers) contained in the resin molded product.
Furthermore, NPL 1 discloses a technique that acquires an X-ray CT image of a woven fabric, in which fiber bundles are woven, by capturing the image using an X-ray CT scanner and performs calculation by using a special filter function on this X-ray CT image, thereby analyzing the orientation of each one of fibers constituting the fiber bundles.